The ubiquitous exposure to environmental contaminants in the US population, combined with the accumulating evidence of immediate and latent harm caused by in utero exposures, increases the need to better understand fetal exposure to chemicals during key stages of development. For most environmental chemicals, studies that examine the relationship between maternal and fetal exposure prior to birth are scarce, largely due to the challenges of collecting biological specimens, in particular umbilical cord blood and amniotic fluid. Meanwhile, questions about the degree to which chemicals cross the placenta, accumulate in the fetus and are metabolized by the pregnant woman and fetus remain unanswered. There is a critical need for human studies that are designed specifically to answer these questions. In this project we will generate unprecedented data on chemical exposures during the second trimester of pregnancy, when certain aspects of fetal development are particularly vulnerable to disruption. Specifically, we will 1) describe fetal and maternal exposure to BPA during the second trimester of pregnancy, and 2) explore the feasibility and accuracy of using maternal biological monitoring results to predict fetal exposure. To do this, we will initiate the collection of maternal and fetal biological specimens from women undergoing elective second-trimester pregnancy terminations. We will measure, analyze and compare levels of the chemical bisphenol A (BPA) in these samples, including a comparison of maternal and fetal metabolism of BPA. The data produced by this research project will fill key gaps in our understanding of fetal exposure to and capacity to detoxify BPA. These findings will inform and strengthen future studies of BPA effects on fetal development. In addition, with the successful implementation of this study, we will be poised to rapidly broaden the PEEC Formative Center to explore exposure to and effects of other important environmental contaminants.